1. Field
The present disclosure relates to light emitting devices, and more particularly, to a light emitting diode source with a protective barrier.
2. Background
A light emitting diode (LED) is a semiconductor material impregnated, or doped, with impurities. These impurities add “electrons” and “holes” to the semiconductor, which can move in the material relatively freely. Depending on the kind of impurity, a doped region of the semiconductor can have predominantly electrons or holes, and is referred to as N-type or P-type semiconductor regions, respectively. In LED applications, the semiconductor includes an N-type semiconductor region and a P-type semiconductor region. A reverse electric field is created at the junction between the two regions, which cause the electrons and holes to move away from the junction to form an active region. When a forward voltage sufficient to overcome the reverse electric field is applied across the P-N junction, electrons and holes are forced into the active region and combine. When electrons combine with holes, they fall to lower energy levels and release energy in the form of light.
LEDs have traditionally been packaged in through-hole or surface mount package configurations. An example of a through-hole package includes an LED encased in a cylindrical or dome shaped lens with anode and cathode leads connected to the LED and extending through the bottom of the lens. These LED packages are often mounted to a circuit board with other LED packages and/or electronic components. For example, an LED driver circuit may be mounted to the circuit board and connected to any number of LED packages to provide an LED light source as an incandescent or fluorescent lamp replacement. As another example, various processing components mounted to the circuit board may be connected to an LED package to provide an indication to an observer of some processing condition or state.
An LED package may be mounted to a circuit board and connected to other LED packages and/or electronic components using various electrical connectors. By way of example, an LED package may be connected to a terminal mounted on the circuit board via an electrical trace and one or more other LED packages and/or electronic components may also be connected to the terminal. As another example, the LED package may be connected to one or more other LED packages and/or electronic components via a wire soldered to a pad connected to the LED package by an electrical trace.
In various lighting applications, such as exterior lighting, refrigeration, damp environment, automotive, trucking, and other harsh environments, a potting material may be applied to the circuit board or light source assembly to protect the electronic components, electrical connectors and electrical traces from moisture intrusion. The potting material, however, is not an optical compound, and therefore, should not obstruct the optical path of the light emitted from the LED. If the optical path is obstructed, a significant reduction in light output and/or a change in color of the emitted light may occur.
As LED packages continue to evolve, it has become increasingly more difficult to apply a potting material to a circuit board without detracting from the optical properties of the LED. The trend in LED packaging has been toward thinner and smaller LED packages. In some cases, such as the so called chip on board (COB) or LED Array approach, the package has been significantly minimized or removed completely, resulting in very small form factor packaging with minimum height. Typical methods of applying potting compounds do not work well with such thin packages with minimal protection of the semiconductor chips, resulting in obstructions of the optical path and loss of light. Accordingly, there is a need in the art for improved methods for applying potting material to such packages or modifications to such packages to enable potting without covering the optical emitting area of the LED, especially as package heights continue to decrease.